<!DOCTYPE html>
<html lang="en">
	<head>
		<title>three.js webgl - geometry - terrain</title>
		<meta charset="utf-8">
		<meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
		<style>
			body {
				color: #61443e;
				font-family:Monospace;
				font-size:13px;
				text-align:center;

				background-color: #bfd1e5;
				margin: 0px;
				overflow: hidden;
			}

			#info {
				position: absolute;
				top: 0px; width: 100%;
				padding: 5px;
			}

			a {

				color: #a06851;
			}

		</style>
	</head>
	<body>

		<div id="container"><br /><br /><br /><br /><br />Generating world...</div>
		<div id="info"><a href="http://threejs.org" target="_blank" rel="noopener">three.js</a> - webgl terrain demo<br />(left click: forward, right click: backward)</div>

		<script src="../build/three.js"></script>

		<script src="js/controls/FirstPersonControls.js"></script>

		<script src="js/ImprovedNoise.js"></script>
		<script src="js/WebGL.js"></script>
		<script src="js/libs/stats.min.js"></script>

		<script>

			if ( WEBGL.isWebGLAvailable() === false ) {

				document.body.appendChild( WEBGL.getWebGLErrorMessage() );
				document.getElementById( 'container' ).innerHTML = "";

			}

			var container, stats;

			var camera, controls, scene, renderer;

			var mesh, texture;

			var worldWidth = 256, worldDepth = 256,
				worldHalfWidth = worldWidth / 2, worldHalfDepth = worldDepth / 2;

			var clock = new THREE.Clock();

			init();
			animate();

			function init() {

				container = document.getElementById( 'container' );

				camera = new THREE.PerspectiveCamera( 60, window.innerWidth / window.innerHeight, 1, 20000 );

				scene = new THREE.Scene();
				scene.background = new THREE.Color( 0xbfd1e5 );

				controls = new THREE.FirstPersonControls( camera );
				controls.movementSpeed = 1000;
				controls.lookSpeed = 0.1;

				var data = generateHeight( worldWidth, worldDepth );

				camera.position.y = data[ worldHalfWidth + worldHalfDepth * worldWidth ] * 10 + 500;

				var geometry = new THREE.PlaneBufferGeometry( 7500, 7500, worldWidth - 1, worldDepth - 1 );
				geometry.rotateX( - Math.PI / 2 );

				var vertices = geometry.attributes.position.array;

				for ( var i = 0, j = 0, l = vertices.length; i < l; i ++, j += 3 ) {

					vertices[ j + 1 ] = data[ i ] * 10;

				}

				texture = new THREE.CanvasTexture( generateTexture( data, worldWidth, worldDepth ) );
				texture.wrapS = THREE.ClampToEdgeWrapping;
				texture.wrapT = THREE.ClampToEdgeWrapping;

				mesh = new THREE.Mesh( geometry, new THREE.MeshBasicMaterial( { map: texture } ) );
				scene.add( mesh );

				renderer = new THREE.WebGLRenderer();
				renderer.setPixelRatio( window.devicePixelRatio );
				renderer.setSize( window.innerWidth, window.innerHeight );

				container.innerHTML = "";

				container.appendChild( renderer.domElement );

				stats = new Stats();
				container.appendChild( stats.dom );

				//

				window.addEventListener( 'resize', onWindowResize, false );

			}

			function onWindowResize() {

				camera.aspect = window.innerWidth / window.innerHeight;
				camera.updateProjectionMatrix();

				renderer.setSize( window.innerWidth, window.innerHeight );

				controls.handleResize();

			}

			function generateHeight( width, height ) {

				var size = width * height, data = new Uint8Array( size ),
					perlin = new ImprovedNoise(), quality = 1, z = Math.random() * 100;

				for ( var j = 0; j < 4; j ++ ) {

					for ( var i = 0; i < size; i ++ ) {

						var x = i % width, y = ~ ~ ( i / width );
						data[ i ] += Math.abs( perlin.noise( x / quality, y / quality, z ) * quality * 1.75 );

					}

					quality *= 5;

				}

				return data;

			}

			function generateTexture( data, width, height ) {

				var canvas, canvasScaled, context, image, imageData, vector3, sun, shade;

				vector3 = new THREE.Vector3( 0, 0, 0 );

				sun = new THREE.Vector3( 1, 1, 1 );
				sun.normalize();

				canvas = document.createElement( 'canvas' );
				canvas.width = width;
				canvas.height = height;

				context = canvas.getContext( '2d' );
				context.fillStyle = '#000';
				context.fillRect( 0, 0, width, height );

				image = context.getImageData( 0, 0, canvas.width, canvas.height );
				imageData = image.data;

				for ( var i = 0, j = 0, l = imageData.length; i < l; i += 4, j ++ ) {

					vector3.x = data[ j - 2 ] - data[ j + 2 ];
					vector3.y = 2;
					vector3.z = data[ j - width * 2 ] - data[ j + width * 2 ];
					vector3.normalize();

					shade = vector3.dot( sun );

					imageData[ i ] = ( 96 + shade * 128 ) * ( 0.5 + data[ j ] * 0.007 );
					imageData[ i + 1 ] = ( 32 + shade * 96 ) * ( 0.5 + data[ j ] * 0.007 );
					imageData[ i + 2 ] = ( shade * 96 ) * ( 0.5 + data[ j ] * 0.007 );

				}

				context.putImageData( image, 0, 0 );

				// Scaled 4x

				canvasScaled = document.createElement( 'canvas' );
				canvasScaled.width = width * 4;
				canvasScaled.height = height * 4;

				context = canvasScaled.getContext( '2d' );
				context.scale( 4, 4 );
				context.drawImage( canvas, 0, 0 );

				image = context.getImageData( 0, 0, canvasScaled.width, canvasScaled.height );
				imageData = image.data;

				for ( var i = 0, l = imageData.length; i < l; i += 4 ) {

					var v = ~ ~ ( Math.random() * 5 );

					imageData[ i ] += v;
					imageData[ i + 1 ] += v;
					imageData[ i + 2 ] += v;

				}

				context.putImageData( image, 0, 0 );

				return canvasScaled;

			}

			//

			function animate() {

				requestAnimationFrame( animate );

				render();
				stats.update();

			}

			function render() {

				controls.update( clock.getDelta() );
				renderer.render( scene, camera );

			}

		</script>

	</body>
</html>
